Masters Degrees (Civil Engineering)

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    Evaluating five mine residue disposal facility case studies using a limit equilibrium method of slices.
    (Stellenbosch : Stellenbosch University, 2024-03) Greyling, Deon; MacRobert, Charles; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    ENGLISH ABSTRACT: In this study, five slope failure case studies, associated with mine waste facilities, such as Tailings Storage Facilities and Waste Rock Dumps, are evaluated using the Morgenstern-Price Limit Equilibrium Method of Slices. The available information of each study has been studied and key information about its investigation, soil test work, pre-failure slope geometry, and the piezometric surface have been extracted to develop a set of limit equilibrium slope stability models. The models were used to search for the critical slip surface and to back-calculate the shear strength of the critical soil region that satisfies a computed factor of safety of unity. The critical slip surfaces, determined from the limit equilibrium models, closely resemble the observed performance of the studied slopes. The back-calculated shear strength parameters of the critical soil region are compared to shear strength parameters derived from laboratory test results and typical values published in the literature. The back-calculated values compared well to the shear strength values published in the literature for similar soils. However, in two cases the back-calculated values did not compare well to values derived from laboratory test results. In both cases, direct shear tests were completed on fine-grained soil, which may have led to erroneous results. In two case studies, the back-calculated values compared well to the test results, and in another, the back-calculated shear strength is between the peak and residual shear strengths derived from laboratory test results. For three case studies, an additional analysis was done where two empirical correlations was used to specify the fully softened shear strength and residual shear strength of finegrained soil. The results of the slope stability models showed that the stability of the slopes is sensitive to the porewater pressure regime, emphasising that it should always be appropriately accounted for in the analysis of a slope that has a consequence of failure. Furthermore, the results of the analyses highlight that the engineering properties of the soils comprising the slope and its foundation should be sufficiently characterised and verified through appropriate geotechnical laboratory and in situ test work. The analyses affirm that the Morgenstern-Price Limit Equilibrium Method of Slices is a suitable tool to investigate slope stability provided that the piezometric surface, soil parameters and slope geometry are accurately defined.
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    Development and testing of an automated time-motion detector for construction activities
    (Stellenbosch : Stellenbosch University, 2024-02) Meyer, Ewald Mauritz; Wium, Jan; Jurgens, Chris; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    ENGLISH ABSTRACT: This study looked into the intricacies of construction rework and the methods that have been used to identify, quantify and manage rework. From this research, a novel process of combining equipment, software and methodology is presented in the development of a concept of an automated time-motion detector system, with a proposed method to implement the system to quantify rework of structural elements on construction sites. The aim of this study is to develop and test a technological solution to detect time spent on construction activities and ultimately uncover un-announced rework on construction sites. This is achieved by completing the following objectives: (i) Determine the most feasible technological solution for the time-motion monitoring of construction activities that could lead to quality failures. (ii) Develop a time-motion detector that can be used to monitor construction activities remotely. (iii) Implement and test the system by performing simplified tests in a controlled environment to determine the accuracy of the system. (iv) Discuss results and future implementations. The motivation for this study was based on the challenge of efficient construction management and the inability to learn from quality failures on construction sites resulting from a lack of suitable data and documentation relating to the execution of construction activities. This lack of execution information hinders construction companies to become more efficient and profitable. In research, a shift is seen towards the gathering and analysis of data to improve the efficiency and profitability of construction companies after very successful implementation of data analysis and management in other fields of study. In this study, a proof of concept of an automated time-motion detector was developed in Python to record and analyse construction activities to determine the human capital required for these activities. The system was tested with several trial tests, where it was found that the system has an average accuracy of 84% while valuable operational data, limitations and recommendations for the use of this system were obtained.
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    Development and automation of an electronic H-TRIS fire testing system
    (Stellenbosch : Stellenbosch University, 2024-02) van Wyk, Ryno; Walls, Richard Shaun; Devine, Courtney; Streicher, Dirk; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    ENGLISH ABSTRACT: In this research a fire testing method, named the Heat-Transfer Rate Inducing System (HTRIS) using electric Radiant Panel Arrays (RPAs), is developed, automated and characterised. An investigation is conducted to study the suitability and benefits of the testing method in the field of fire engineering, as it is not currently a standard testing method. An existing H-TRIS has been developed and consists of propane-fired radiant panels mounted to a frame with a linear stepper motor controlling the emitting heat of the system. In contrast, the electronic H-TRIS (eH-TRIS) developed in this study comprises electric radiant panels mounted to a frame with the temperature of the radiant panels controlling the emitting heat of the system. The system is developed by designing and building (1) the experimental setup and (2) the control box of the testing method. The experimental setup consists of the radiant panels mounted to a trolley, and the control box comprises the hardware and electrical components used to control the system. The system is automated by developing a feedback control system which controls the temperature of the radiant panels based on the power supply. A Graphical User Interface (GUI) is developed to specify the system inputs and configuration parameters. The system is characterised by measuring the heat flux received at various positions at specified separation distances from the radiant panels. Based on operational tests conducted, an empirical model is developed to predict the heat flux received on a surface at a specified distance from the radiant panels. Similar to the cone calorimeter, the system is calibrated to ensure accuracy over time. The eH-TRIS enables the simulation of the behaviour of materials or systems experiencing different heat sources - a real fire, furnace test, or specified thermal boundary conditions of a fire model. This eH-TRIS ensures reproducible results at a relatively low cost compared to furnace tests. The contribution of this study is (1) the development and automation of an H-TRIS using electric RPAs (eH-TRIS), and (2) the quantification of the spatial heat flux variation on a receiving surface tested with the eH-TRIS. The advantage of the system is that the heat fluxes emitted can be controlled more accurately, more consistent spatial variations in heat flux can be produced, laboratory safety is improved and the system is adaptable to different configurations and setups. The primary disadvantage of the system is that it reaches lower maximum heat fluxes relative to gas burner setups. The affordability, the quick setup of tests and the variety of materials that can be tested, presents the H-TRIS as one of the more successful testing methods for modelling information.
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    Back analysis of foundation performance case studies
    (Stellenbosch : Stellenbosch University, 2024-02) Heynes, Callen; MacRobert, Charles; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    ENGLISH ABSTRACT: When dealing with foundation design, geotechnical engineers deal with a significant degree of uncertainty, given the complex nature of the soil. The uncertainty associated with a project cannot be completely removed. However, it can be adequately reduced by obtaining a better understanding of the material. All design decisions need to be based on the knowledge of the material to ensure that adequate measures are incorporated into the design to mitigate associated risks and uncertainties. While understanding the material, geotechnical engineers also need to exhibit sound engineering judgement and experience. This can take time to develop, something that engineers do not have. However, engineers can use case studies in situations similar to their own to learn from more experienced engineers and understand how they approached a similar problem. This study looked at case studies that dealt with shallow foundations. The information regarding these foundations was presented as a structured case study abstract. Information such as the location, soil profile, foundation solution, and loading conditions were all highlighted in the abstracts. In the current study, the settlement performance of the foundations was analysed using Settle3. This method of analysis was used as the case studies considered utilized older methods of analysis. Settle3 is a foundation analysis software, that enables quick analysis of the foundations. The software utilized several empirical methods to predict the settlement. The settlements determined using the software were compared with the predictions made by the authors of the original study. The predictions made in the original and the current study were shown in the abstracts. Assumptions made were regarding the homogeneity and the stressstrain relationship of the soil. The results obtained in the original studies generally overestimated the observed settlement of the foundations. The analysis done in this study utilized the same assumptions made in the previous studies. However, the results were closer to the actual displacements but still overestimated them. The case study abstracts documented relevant information regarding the settlement performance of the shallow foundations in a single, accessible document. Practicing engineers should be able to access these abstracts and use them to supplement their knowledge and experience with the knowledge of other engineers. In so doing, they can look to implement the successful aspects of a project while looking to avoid the same mistakes. Therefore, utilizing the case study abstracts will help to ensure the timely delivery of a successful project. A database containing these case study abstracts is yet to be formed.
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    Demonstrating the value of case histories towards the improvement of knowledge and understanding of geotechnical problems using slope stability back-analysis.
    (Stellenbosch : Stellenbosch University, 2024-03) Wright, Gary; MacRobert, Charles ; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    ENGLISH ABSTRACT: This thesis sought to demonstrate the benefits of utilizing case histories as tool for the improvement of knowledge and understanding of geotechnical problems. For the purposes of demonstration, the problem of slope stability was considered. Four case histories and one original study concerning natural slope failures were selected and subjected to a stability back-analysis. Summaries and geotechnical models were created for each failure using information extracted from the respective case history, its cited sources, provided raw data, and Google Earth. The first failure considered a circular slip through colluvial material following heavy rain which damaged five properties in Camps Bay, South Africa. Study of the failure suggested that the slope was destabilised due to slope steepening during property development. Failure was then triggered due to water infiltration which resulted from a combination of heavy rainfall and an unmaintained stormwater inlet. An iterative back analysis was used to determine the shear strength parameters of the colluvial material at the time of failure. The results were validated by comparing the failure surface estimated by analysis software against the slip surface estimated through interpretation of surveyed movement monitoring data. The second failure considered a circular slip through alluvial material which damaged forty-five properties in Mossel Bay, South Africa. Back-analysis suggested the failure to be the result of an underlying weaker layer. This was supported by the results of a 2D and 3D analysis which predicted the critical failure surface, and many potential failure surfaces, to pass through the weaker layer. The third failure considered the shallow slip of a valley slope following heavy rain which damaged an athletic track in Shillong, India. Back-analysis suggested the failure to be the result of water infiltration introducing porewater pressures into the slope. A combined transient seepage and slope stability analysis using rainfall data was used to model the failure. Analysis results compared well to the actual failure. The fourth failure considered a circular slip through a riverbank comprised of clay in Drammen, Norway. A detailed 2D model was subjected to an Effective Stress analysis as well as a Total Stress analysis. Result of the Effective Stress analysis produced a Factor of Safety equal to approximately 1 while the Total Stress analysis produced a Factor of Safety below 1. Therefore, the Effective Stress analysis was determined to be the more accurate. Further analysis suggested that the slope was destabilized due to a low river level and triggered by the placing of fill material at the edge of the riverbank. The fifth failure considered debris flows following heavy rain which caused severe damage and loss of life in Chimanimani, Zimbabwe. The original study of the failure suggested that the slopes of Chimanimani were particularly sensitive to changes in ground water conditions. Results of a combined seepage and slope stability analysis suggested that the failures were the result of porewater pressures being introduced into the slope. The findings of the respective back-analyses were further considered for identification of common factors influencing failure. Slope destabilization and failure among the five studies was commonly attributed to changes in porewater pressure and those human or natural activities which change the geometry of the slope. The findings of this thesis suggest that these factors be given particular attention when performing a slope stability analysis. Furthermore, this thesis stresses the importance of performing a site investigation prior to development of natural slopes. Site investigations allow for the early detection of geotechnical problems which may then be addressed during the design phase.